Keeping the depth of anaesthesia and analgesia within clinical target could be one of the major preventative methods as it has been speculated that anaesthetic agents and PD may be neurotoxic and have long-term neurologic consequences to the developing brain.([FOOTNOTE=Salaün JP, Poirel N, Dahmani S, Chagnot A, Gakuba C, Ali C, Gérard JL, Hanouz JL, Orliaguet G, Vivien D. Preventing the Long-term Effects of General Anesthesia on the Developing Brain: How Translational Research can Contribute. Neuroscience. 2021 May 1;461:172-179. doi: 10.1016/j.neuroscience.2021.02.029.],[ANCHOR=],[LINK=]) In addition, the intraoperative combination of assessing the depth of anaesthesia as well as measuring the patient’s nociceptive state improves the safety and quality of recovery, including lowering the occurrence of postoperative delirium.

Prevention Strategies for Postoperative Delirium

According to published studies, postoperative delirium is preventable in up to 40% of cases.([FOOTNOTE=Fong, T. G., Tulebaev, S. R. & Inouye, S. K. reviews Delirium in elderly adults : diagnosis , prevention and treatment. Nat. Rev. Neurol. 5, 210–220 (2009).],[ANCHOR=],[LINK=]) Which, highlights and concludes the importance of delirium screening throughout the entire process within the perioperative setting.


I. Preoperative Assessment for Postoperative Delirium

During the preoperative evaluation, physicians and nurses need to look for early indicators of postoperative delirium (POD), such as cognitive deficits (including hyposmia), sleep disorders and subjective memory impairment. Knowledge of predisposing and precipitating factors are vital for physicians to tailor their treatment strategy to reduce the incidence and harms of POD.([FOOTNOTE=Menzenbach, J. et al. Estimating patients ’ risk for postoperative delirium from preoperative routine data - Trial design of the PRe-Operative prediction of postoperative DElirium by appropriate SCreening ( PROPDESC ) study - A monocentre prospective observational trial. Contemp. Clin. Trials Commun. 17, (2020).],[ANCHOR=],[LINK=]) In addition, it is also recommended to introduce a rehabilitation program for high-risk patients. Such programs include exercise and nutritional and psychological support, all of which have demonstrated effectiveness in decreasing the occurrences of POD.([FOOTNOTE=],[ANCHOR=],[LINK=]),([FOOTNOTE=Gual N, García-Salmones M, Brítez L, et al. The role of physical exercise and rehabilitation in delirium. Eur Geriatr Med. 2020;11(1):83-93. doi:10.1007/s41999-020-00290-6],[ANCHOR=],[LINK=])

II. Intraoperative Monitoring of Anaesthesia

Intraoperative neuromonitoring is imperative to avoid unnecessarily deep anaesthesia that may increase the risk of postoperative delirium.([FOOTNOTE=Wernecke, K. D. & Spies, C. D. Monitoring depth of anaesthesia in a randomized trial decreases the rate of postoperative delirium but not postoperative cognitive dysfunction. Br. J. Anaesth. 110, 98–105 (2013).],[ANCHOR=],[LINK=]) Measuring the depth of anaesthesia results in decreasing anaesthetic exposure and encouraging quicker neurological recovery, which subsequently reduces POD incidence.([FOOTNOTE=Tomlinson, J. H. & Partridge, J. S. L. Preoperative discussion with patients about delirium risk : are we doing enough ? Perioper. Med. 5–8 (2016) doi:10.1186/s13741-016-0047-y.],[ANCHOR=],[LINK=])

Preventing postoperative delirium is the best approach to avoid further postoperative complications. To this end, Medtronic provides a device called Bispectral Index™ Brain Monitoring System (BIS), which is a proprietary system that evaluates the EEG while the patient is sedated, displaying a value between 0 and 100 that clinicians can use to assess the depth of anaesthesia in a patient. In addition, Medtronic suggests combining the BIS™ Brain Monitoring System, which measures the depth of anaesthesia and can be used to guide the administration of anaesthetic agents, together with the NOL® PMD200 Nociception Monitor, which monitors pain levels and guides the administration of analgesia during surgery, to improve patient safety and promote faster recovery.

Monitoring Solutions to Reduce the Incidence of Postoperative Delirium

The Bispectral Index™ guided anaesthesia has been shown to reduce the risk of developing POD.([FOOTNOTE=Chan MT, Cheng BC, Lee TM, Gin T; CODA Trial Group. BIS-guided anesthesia decreases postoperative delirium and cognitive decline. J Neurosurg Anesthesiol. 2013;25(1):33-42.],[ANCHOR=],[LINK=]) Compared to routine care, administering total intravenous anaesthesia (TIVA) guided by the BIS™ Brain Monitoring System was shown to reduce propofol use by 23%, emergence time by 34-38%, and PACU discharge time by 16%.([FOOTNOTE=Gan, T. J. et al. Bispectral Index Monitoring Allows Faster Emergence and Improved Recovery from Propofol, Alfentanil, and Nitrous Oxide Anesthesia. Anesthesiology 87, 808–815 (1997).],[ANCHOR=],[LINK=]) Moreover, the updated BIS™ Monitoring System software version 3.5 is now available.
The NOL® PMD200 and the BIS™ Brain Monitoring System with its new version 3.5 software are available to anaesthesiologists and the anaesthesia care team to help prevent administering excessive or insufficient levels of anaesthesia. According to the results of studies, using BIS™ monitoring to guide TIVA anaesthesia decreases confirmed awareness by up to 78%([FOOTNOTE=Zhang, C. et al. Bispectral index monitoring prevent awareness during total. Chin Med J 124, 3664–3669 (2011).],[ANCHOR=],[LINK=]) and may be associated with reduced use of anaesthetics, quicker cognitive recovery and the reduction in risk of POD by up to 35%.8


III. Screening for Postoperative Delirium

Nurses play a vital role in identifying symptoms of postoperative delirium in patients, as they provide around the clock care for patients and are often first to notice a change in a patient’s behaviour. Moreover, it is important to note that delirium is usually reversible; hence, early diagnosis is essential to effectively reverse the condition.2 If treatment is delayed, recovery can have serious consequences for the patients and their caregivers, such as permanent functional and cognitive decline.2 Therefore, it is imperative to screen patients for signs of POD at least daily, if not more frequently, paying particular attention to higher risk patients.3 It is best to assess patients with formal questions such as the digit span, days of the week or months of the year backwards or serial 7s (counting down from 100 by 7). For optimal diagnosis, combining these questions with thorough observations is recommended to thoroughly assess the patient for signs of delirium.([FOOTNOTE=Kostas, T. R. M., Zimmerman, K. M. & Rudolph, J. L. Improving Delirium Care : Prevention , Monitoring , and Assessment. The Neurohospitalist 3, 194–202 (2012).],[ANCHOR=],[LINK=])